Multiplex communications – Wide area network – Packet switching
Patent
1990-10-30
1992-08-25
Safourek, Benedict V.
Multiplex communications
Wide area network
Packet switching
370 851, 455 51, H04J 324, H04H 108
Patent
active
051425327
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND
1. Field of the Invention
The invention relates to communication systems and to such systems employing a passive network, for example a passive optical network. Such passive networks control the operation of the network at the local exchange or head end for a number of customers.
2. Prior Art and Other Considerations
For telephone companies, optical fibres have the capacity to handle a range of services beyond telephony.
In the past, coaxial cable TV networks have, in the main, been used totally separately from the telephone network. It is now becoming clear that beyond the development of the switched-star network and improved advanced optical fibre technology, there is a need for a more flexible telephony based system with additional services provided.
SUMMARY
The present invention is concerned with a configuration capable of producing an enhanced service capability typically on a local fibre network using passive networks employing optical splitting to reduce and share costs.
According to the invention there is provided a bidirectional broadband and telephony network controllable from the exchange or head end of the network including means at the exchange or head end for allocating time slots for information packets to travel without interference to and from a plurality of receiving stations, wherein the allocating means includes means for determining the round-trip delay between the exchange or head end and each of the receiving stations and means for adjusting the round trip delay to ensure correct spacing of the information packets during passage through the network, and includes means for interrogating stations and enforcing allocation thereto to ensure each stations minimum bandwidth requirements are fulfilled, and means for dynamically allocating spare capacity to each station for bursty services.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be described by way of example with reference to the accompanying drawings in which:-
FIG. 1 shows a network configuration capable of handling telephony and broadband services eg broadcast TV).
FIG. 2 shows one example of the frame structure of the telephony channel of FIG. 1.
FIG. 3 shows an expanded configuration capable of handling broadband dialogue services.
FIG. 4 shows the customer end configuration of the ATD channel.
FIG. 5 shows the customer equipment of FIG. 4 in more detail;
FIG. 6 shows the exchange end block 40 in more detail;
FIG. 7 shows the `d` value controller of FIG. 6 in more detail;
FIG. 8 shows a modified frame structure of the telephony channel to accommodate the ATD control information; and
FIG. 9 shows the cell structure of FIG. 3.
DETAILED DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a proposed configuration for a passive optical network. The exchange telephony block 10 provides telephony at a rate typically 20 Mbit/s on one wavelength (.lambda.1) and the TV block 11 provides broadcast TV on a second wavelength (.lambda.2) and these pass to the local exchange end 15.
A single mode optical fibre (16) is fanned out to a number of customers premises (30, 31) via passive optical splitters (17, 18) located at the cabinet (c) and street Distribution Point (DP) positions respectively, for example. An 8-way split is allowable at the cabinet and a 16-way split at the DP. However, the maximum amount of splitting is selected to be 32 to keep within the optical power budget available for broadband bit-rates in this particular configuration.
For customers requiring telephony only, current system design views are favoring a network which features a maximum optical split up to 128 ways and a highest bitrate of operation of 20 Mbit/s. This bitrate/split combination allows an attractive set of options for both business and residential customers. At the maximum split of 128 (120 customers plus 8 test ports), capacity would be available to feed each customer, if desired, with an ISDN 144 bit/s channel or equivalent capacity. For business districts, where multiple line customers are in the majority, a lower optical split would be emp
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British Telecommunications public limited company
Hsu Alpus H.
Safourek Benedict V.
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